The intent of this project is to characterize cell surface antigens associated with human leukemia by means of allogeneic and xenogeneic antisera. By use of both manual and automated immunofluorescence and cell separation techniques, we will study the specificity of antisera against different leukemia cell types; changes in antigenicity during the course of the illness; and the use of antisera for immunodiagnosis of minimal leukemic disease. These sera will also be used as reagents to aid in biochemical identification of radioactively labeled leukemia antigens.